Abstract E cigarettes (E-cigs) are increasingly popular worldwide, in particular, among youths. E-cigs may contribute to nicotine addiction and are unlikely to discourage conventional cigarette smoking. Mainstream and second-hand E-cig aerosols contain, in addition to nicotine, detectable levels of toxins including carcinogens and heavy metals such as formaldehyde, benzene, nitrosamines, cadmium and lead. Therefore health risk and toxicology studies on animal models exposed to E-cig aerosol, not limited to nicotine, are urgently needed. We propose to develop a system designed for E-cig exposure to rodent models. With the support of our NIDA/NIH Phase I grant, we designed and built ten prototypes including hardware and software that control 3-4 E-cigs and timing of activation that can simulate the vaping pattern of E-cig users. We have characterized the aerosol particle size distribution and mass concentration in the breathing zone of the rodent exposure chamber. We have tested the prototype with acute and chronic rodent experiments. We have optimized the parameters of aerosol exposure and showed that the system can generate rodent models with nicotine circadian pharmacokinetics resembling human E-cig users. This application is to further develop and commercialize the product line for the E-cig research community. Aim 1. To build, upgrade and commercialize the product line of efficient E-cig aerosol generation and exposure systems delivering E-cig aerosol to rodents through inhalation with characteristics equivalent to those inhaled by human E-cig users. We will upgrade the system to integrate our ValveLink 8.2 technology. With USB connections, a computer can independently control up to 64 channels at 5-6 channels per animal exposure chamber. We will make E-cig holders for different E-cigs available in the marketplace including the NIDA standardize research E-cigarette (SREC). We will incorporate a Collison nebulizer to generate saline aerosol for control. We will make a product for rodent E-cig self-administration for studying addiction that includes software controlling two nose-poke sensors that either activate E-cigs or control aerosol when poked. Aim 2. To validate the E-cig aerosol generation and exposure system with acute and chronic animal experiments that produce E-cig exposure animal models for a variety of research needs including the study of addiction. We will test the system with behavioral experiments such as conditioned place preference (CPP), withdrawal signs with chronic intermittent E-cig exposure and E-cig self-administration experiments in rodents (rats or mice). In addition to validating the device, these experiments are significant in understanding E-cig reinforcement and dependence. Our products will meet the needs of the E-cig research community and advance the field to enable testing potential toxicities of E-cigs in animal models as well as facilitate new therapeutic discovery e.g., for nicotine addiction. Our products will be a powerful tool for studying the effects of E-cig vaping on the cardiovascular, respiratory and nervous systems, on metabolism, carcinogenesis, pregnancy and teratogenicity as well as their underlying mechanisms.